Orb Weaver - Araneus - BugGuide.Net

Moved

Moved from Spiders.

… Alice Abela, 14 February, 2015 - 11:59am

Ah! These are so frustrating!

Just when we think we understand something, it slips away. Even with all these examples, we can't quite get the abdomen color pattern or the eye patterns to make sense.
Some with indistinct humps and the white outline edging coming right down from them across the anterior of the abdomen

seem clearly to be montereyensis.
Some with distinct humps and the white edging staying high on the abdomen giving a uniform dark anterior abdomen

seem clearly to be bispinosus.
But then we stumble on to ones such as this...
We were tempted to say montereyensis just as

So we looked at the Manolis illustrations and just started laughing. It looks like he used the exact same illustration for both and just colored one darker!!
We imagine there is something that will make this easier, but we haven't found it yet. Sorry

… john and jane balaban, 10 February, 2015 - 11:12am

Eyes

Looking at

, the eyes on her seem to me to be as far apart as those on A. bispinosus, but A. montereyensis is supported by a good ventral

. I'm frustrating myself on these too!

… Alice Abela, 14 February, 2015 - 12:05pm

Pattern

I'm thinking that one will not be able to go by pattern at all on these. I'm seeing a lot of variation. So far, all of the females I've gotten good ventral shots of have been A. bispinosus. The prominence of the humps also really seems to vary with how well fed/fat the spider is. The pattern can also be misleading as the white seems to accentuate the humps a bit. Angle of the photo can also make a big difference.

I'd be inclined to treat each spider without a good scape shot for females or pedipalp shot with the males with a grain of salt in terms of ID. I'm not seeing a clear difference in eye spacing either on the bugguide images and am wondering if some may be misfiled and this is complicating the issue.

Maybe for the sake of consolidation/organization an A. montereyensis/bispinosus page could be added to file all of the undetermined spiders (kind of like for the Common or White Checkered Skipper: http://bugguide.net/node/view/354354/tree )?

Also for A. monteryensis epigyne shots for:

and

look really different.

I also have

who doesn't seem to fit in quite with either species given her size. I don't know what the chances are that there is something undescribed hanging around too.

… Alice Abela, 10 February, 2015 - 7:25pm

Not near our books right now

Will check in on these and see what we can learn when we get the opportunity

… john and jane balaban, 21 January, 2015 - 9:50pm

Moved

Moved from ID Request.

… Lynette Elliott, 26 February, 2014 - 8:22pm

Any more images from different perspectives?

montereyensis and bispinosus are sometimes collected together so habitat won't help us. Anterior median eyes three diameters apart in bispinosus. 1.5 diameters apart in montereyensis. Abdomen is triangular wider than long with a slight hump anteriorly on each side for bispinosus. Abdomen is sub triangular with indisticnt humps in montereyensis. Levi says "The females of montereyensis differ from those of bispinosus by having less distinct humps on the abdomen." These humps certainly seem distinct.

… john and jane balaban, 25 February, 2014 - 10:08am

Humps do look distinct

I pretty much only have dorsal shots, this is one from a slightly different angle http://www.flickr.com/photos/44150996@N06/12762230055/sizes/l/ if it helps in terms of ID I can upload it to bugguide as well

… Alice Abela, 25 February, 2014 - 12:29pm

But...

Maybe the humps are more distinct because the spider could be "plumper" looking at the full resolution images the anterior median eyes are visible and look to be ~1.5 diameters apart as opposed to three. I'll post a full resolution crop of the eye area tonight.

… Alice Abela, 25 February, 2014 - 2:11pm

A. bispinosis

Looking at the eyes of the females from the same site that are A. bispinosus, I'm thinking she is too. To make the diameters fit it looks like their only going by the dark pigmented area of the eye rather than the unpigmented raised base.

… Alice Abela, 21 January, 2015 - 10:00am

likely,

but the two species may be quite hard to tell apart.

… Lynette Elliott, 21 January, 2015 - 8:10pm

edit

Should have said "they're" rather than "their", so embarrassed :oP

… Alice Abela, 21 January, 2015 - 11:09pm